Sewing-machine mechanism



Oct. 17, 1950 R. K. HOHMANN' 2,':526Q4lf9 .SEWING MACHINE MECHANISM 1N VEN TOR. RIC/m R0 A. Hof/MANN BY l I A TTORNEX Oct. 17, 1950 R. K. HoHMANN SEWING mol-11m; uEcHANxsu- Flea April 6. 1948 s sheets-sheet s 1N VEN TOR. /CHAR@ K Hof/MANN BY WE.

ATTO/Vfx Patented ct.

A'UNI TE D S TATES PAT E. N T O FF IC E 12,526,479 'SEWING-MACHINE MECHANISM .Richard TK. Hohmann, Jamaica, N. Y.

AppiicationApril 6, 1948, Serial No. 19,27 5

(Cl. i12-220) -5C-laims.

l The general object of the present invention is to provide an improved llight-weight portable sewing machine which is of the small size commonly referred to as a little girl sewing machine, and is ch'aracterizedby its mechanical simplicity and its inherently low cost of production, and by its sewing capacity which is approximately equal to that of -a domestic sewing machine of `standard size.

A specic object of the invention is to provide a belt drive connection between an electric motor mounted in the frame base of a chain stitch sewing `machine andthe lower hook shaft of the machine, which includes an intermediate shaft and separate belts connecting the intermediate shaft to the motor and hook shafts, which will permit 0f a speed reducing factor large enough to permit the ymotor to be of a relatively high speed inexpensive type, and which will permit the hand wheel of the sewing machine to be carried by the intermediate shaft and located at a .convenient distance above the baseportion of the sewing machine frame.

In a preferred form of the invention, grooved pulleys carried by the motor shaft and said intermediate shaft, are connected by ,a rubber belt, and a sprocket wheel carried by the intermediate shaft is connected by a sprocket .chain .belt to a sprocket Wheel carried by the underbed hook` shaft, and a crank pin carried by the last mentioned sprocket wheel is connected by a link to a crank arm carried'by .an oscillating needle bar shaft mounted in the hollow arm portion of the frame. Each belt connection, howevenmay comprise a rubber or analogous lbelt running over grooved pulleys .or sprocket chains running over sprocket wheels.

-The various features of novelty whichl characterize my invention are pointed out with particn ularity in the claims annexed to and forming a part of this specification. For a Vbetter understanding ofthe invention, however, its Yadvantages and specific objects attained with its use, reference should be had .to the accompanying-drawing and descriptive matter in which Ihave illustrated and described a preferred embodiment of the invention.

Of the drawings:

Fig. 'l isa sectional elevation ofthe improved sewing machine, the section being taken on the line l-l of Fig. 5;`

Fig. 2 is a plan view ofaportion of the machine shown in Fig. 1;

Fig. 3 is an elevation in sectionon the line A3--3 of Fig. 1;

`tions C3 and C4. 'lower ends ofthe portions C3 and C4 may be em- Fig. 4 is a partial plan section on the line 4 4 of Fig. l; and

Fig. 5 is an elevation in section on the line 5 5 of Fig. 1.

The frame of the sewing machine shown in the drawings comprises a hollow base A open at its bottom,A a hollow standard B extending upward from the base at one end of its work bed portion A', and a hollow arm portion C. Preferably and as shown, the base, standard and arm portions of the frame are integrally connected portions of ka light weight metal casting. The frame metal is advantageously aluminum in the form known as hard aluminum. The arm portion C is formed with an opening C comprising a main portion `extending along the entire upper side oi the arm and depending portions at the front side .of theA needle head portion of the arm and at the opposite end o f the arm. The opening VC isnormally closed by a ,detachable .cover plate C2 lhavi'ng .a horizontal body portion and depending .end por- Screws extending .through the ployed to detachably secure the coverpart to the frame. An. electric motor D is mounted .in vthe hollow base of the sewing machine frame andhas its frame connected to the work Vbed portion yof the base by screws D. The base portion Y.A is provided at .its end remote from the standardB with ay work bed extension A?. The extension A2 may be a steel plate connected to the base A by screws A3.

As shown, most of the .frame of tbe motor D isbene'ath'the work bed portion A .of the .fra-me, butthe motor 'shaft D2 carriesv a small pulley E located beneath the portion rof the standard B remote'from thework bed portionA. Thepulley E drives an intermediate pulley F `throiu'gh a belt G, ordinarily lmade .of rubber. The pulley F is secured to an intermediate, or counter shaft .H which extends hcrizontallythrough the standard B at a level shown as about-midway between-the top side of the base A andthe underside -of Athe arm C. The shaft H is 'journalled in integral interna] boss portions B and B2 of the frame standard B. The boss B projects away fromthe inner side of the left hand portion of the standard B. The boss B2 is carried by an integral web portion B3 of the standard B intermediate its right and 'left hand side portions, as seen in Fig. l. The pulley Fis at the inner side of the sewing machine hand wheel F' which may be formed integrally with said pulley. Advantageously andas shown, however, the hand wheelF is detachably clamped against the end of the hub of the pulley F by a clamping nut H2 on the threaded outer end of the shaft H. The hand wheel F' has a rim portion extended to the standard B and a portion f smalier diameter which extends through a round opening B4 in the adjacent wall of the standard B. With the hand wheel F disconnected from the pulley F, the belt G after being moved laterally oil" the pulleys E and F, can be moved out of the frame through the opening B4.

The shaft l-l is shown as connected through a sprocket chain belt I with the underbed hook shaft J of the sewing machine. At its iront end, the shaft J carries a hook J of a conventional chain stitch machine type. In the preferred construction shown, the belt I runs over a small sprocket wheel K carried 'by the shaft H and a larger sprocket wheel L carried by the shaft J at its rear end. The wheel L and pulley F are detachably secured to the shaft H by set screws, in positions relative to the boss B2 to prevent objectionable longitudinal movement of the shaft H.

In ordinary practice, the motor may well be a 1/50 horsepower motor of a universal, commercially available type adapted to operate when under normal load, at about 5000 revolutions per minute, and to operate at about double that speed when running without load. Such a motor is well adapted for use in driving the sewing machine at the speed required to make about 750 tov 800 stitches per minute, when the pulleys and vwheels E, F, L and K are proportioned substantially as indicated in Figs. 1 and 3, so that the rotative speed of the motor shaft E is a little less `than seven times the rotative speed of the hook shaft I. Such commercially available motors are relatively small and inexpensive.

The sprocket wheel I serves as a crank disc carrying a crank pin L. The latter is connected by a link M to a pivot or crank pin N"2 carried by a crank arm N secured to one end of an oscillating needle bar shaft N horizontally disposed in the sewing machine frame arm C. In the desirable construction form shown, the shaft N is coaxial with and pivotally supported by trunnion pivots N3 which are secured, and are axially adjustable in passages or openings formed in web portions OC and C5 of the arm C adjacent the opposite ends of the latter. The pivots N3 and the shaft N may be made of a suitable hard steel or steel alloy, and the pivots may be large enough in cross-section to avoid any tendency, due to ordinary operating stresses, of the pivots N3, to enlarge the openings in the portions of the aluminum frame arm C in which they are mounted. The use of the trunnion pivots N3 thus makes it unnecessary to mount bearing bushings in the aluminum frame for the shaft N.

The needle bar end of the shaft N carries a crank arm N4 connected through a link N5 to a pivot pin carried by a collar or pivot supporting member Ol which surrounds and is adjustably secured by a set screw O2 to the vertical needle bar O. The latter is mounted in aligned openings formed in a thickened bottom wall portion C6 of the needle bar end of the arm C, and in anupper web portion OC of the arm C. The needle bar Oy is provided at its lower end with means for the attachment to the bar of a needle O2. The up and down movement given the needle bar O` is preferably greater than is customary in chain stitch machines, and is sufficient to permit the use of a needle O2 which is a commercially available, lock stitch type, sewing machine needle.

The needle bar O carries a second vertically adjustable collar member P above the member O which supports a vertical pin P parallel to and alongside the needle bar, and axially movable in an aligned passage formed in the boss OC and in the cover plate C2 between the similarly aligned sets of passages which respectively receive the upper portion of the needle bar O and the upper portion of parallel presser bar Q. As is hereinafter described, the pin P controls the operation of a thread clamp T. The presser bar is provided at its lower end with a presser foot Q', and is biased for down movement to hold the presser foot in engagement with the work. A presser bar lifting lever Q2 is mounted in the needle bar end of the arm C. The presser foot Q, lever Q2 and means biasing the presser bar for down movement may be conventional in form and arrangement.

The thread clamp T, engaged by the pin P', is in the form of an elongated piece of sheet metal having its rear end clamped against the upper side of the body of a sheet metal support for thread tension discs R by the screw S. The latter extends through the clamp T and support S into the removable arm cover member C2. The other end of the spring T extends over the pin P secured to the metal bar O. Adjacent its free end the clamp member is formed with a lateral thread clamping projection T which extends over a corresponding portion S2 of the support S. Except when the needle bar is in or near its uppermost position, the clamping projection T clamps the thread U against the part S2. As the needle bar approaches its uppermost position, however, the pin P engages the front end of the clamping member and raises the clamping projection T so as to permit the thread U to move freely in the direction of its length through the space between the part T and Asupporting part S2. The tension support S is formed with an uprising portion S3 in which one end of a horizontal threaded post or disc support R is anchored. The post R' passes through and supports a pair of apertured tension discs R which frictionally engage the portion of the thread U passing between the discs. The tension with which the thread U is engaged by the discs is due to the action of the helical bias spring R2. The latter surrounds the post R' and acts between the disc R remote from the supporting portion S2, and the adjustable abutment formed by a nut R3 threaded on the post R. As shown, the thread U passes to the tension discs R through a thread guide passage S4 formed in a transversely bent part of the uprising portion S3 of the member S. The thread passes to the passage S4 from a thread spool mounted on a spool support W secured to and extending upward from the cover plate C2 and including a thread guiding disc W larger in diameter than the spool and coaxial with the spool at the end of the latter adjacent the tension discs R. The thread clamping mechanism just described is not claimed herein, but is claimed in my copending application, Ser. No. 122,388, led October 20, 1949, as a division of this application.

The means for advancing the work over the work bed in the sewing operation comprises a feed bar X carrying a feed dog X and formed at one end with an open ended slot X2 through which extends a horizontal supporting shaft X3 anchored in the frame base A. In practice, and as shown, the shaft X3 has a screw head at its outer end and has its other end in threaded engagement with the base A. A spring X4 acting `between the fpin X3, and an abutment. or feed bar -shoulder X5, biases the Yfeed bar for-movement in a direction opposite to the direction of form parallel leg portions X6 spaced away from one ,another by a distance equal to the diameter of a cam or eccentric disc Y secured to the hook shaft J between the hook J and adjacent end wall of theframe base A. The rotation of the member Y acts on the feed bar portions Xs to give the-latter lup Aand downmovements, and acts against a curved bearing surface X7, extending between the legs X6, to give the feed bar movement toward the pin X2 during the feeding.

stroke of the feed bar, and to permit the bar to move tothe right under Vthe action of the spring X4 during the return stroke of the feed bar.

The length of the feeding stroke is controlled by a stop lever Z pivotally connected to the sewing machine frame base A by a pivot pin Z and having a cam edge surface Z2 moved by the angular adjustment .of the lever into, and is then frictionally held in a position in which it is engaged by an abutment portion X of the feed bar, earlier or later in each return movement of the feed bar under the action of the bias spring X3. The member X8 is advantageously in the form of a strip of spring metal having its ends attached by screws to the ends of the feed bar legs X6. The spring strip X8 cushions the engagement of the feed bar with the stop lever Z. No claim is made herein on the special form of the feed bar mechanism disclosed, as that mechanism is disclosed and claimed in my co-pending application Ser. No. 19,276 led concurrently with this application.

As shown, the feed dog X' comprises two side by side horizontally elongated portions X1o with their upper edges serrated, which are received in slots formed in the work bed extension A2. During the feeding stroke of the feeding bar, the feed dog parts have `their serrated upper edges above the level of the upper surface of the work bed extension. During the return or nonfeed stroke of the feed bar, the serrated upper edges of the feed dog parts are lowered into the work bed extension slots.

L carried by the motor shaft and hook shafts,

respectively, and to permit the hand wheel F to be located in a convenient position above the base of the sewing machine frame. With the crank and link connection between'the needle bar shaft and the wheel L rigidly secured to the hook shaft J, the slippage of the belt G over either of the pulleys E and F cannot interfere with the proper timing of the hook and metal bar movement. The hook J is of a well known efficient and inexpensive type, formed from sheet metal. The total amount of machining and in particular, the amount of highly accurate machining required in the production of the sewing machine, is reduced to a practical minimum.

The sewing machine disclosed includes fewer parts than any other sewing machine having equal sewing capacity of which I have knowledge,

and is adapted to Voperate .at/top speed ywith practically no tendency of the machine to creep or walk over the supporting surface. In-the particular form and design of thefmachine illustrated, thehorizontal distance between thefneedle and the adjacent side of the standard B is four inches. The machine shown is `capable-of satisfactory operation in stitching together ftwo .plies or layers of `finev silk fabric, andxinstitching together as many as four plies or layersof heavy canvas. The machine includes no toothedragearing other than the lsprocket wheels K'and`L,and those wheels may be replacedby groovedipulleys, if and when it seems desirable to use .a rubber belt connection instead of a sprocket chain connection between the intermediate shaft `I-I and hook shaft J. The removal of the top `cover member -C2 with its depending face plate and rear end portions C3 and C4, exposes ally of the operating parts of the sewing mechanism 'above the level of the work bed, and thus facilitates'the assembly, inspectionfadjustment and repairwof the mechanism. 'Novel features ,of the .frame construction of the sewing machine illustrated but notV claimed herein, are claimed in' my copending application, Ser. No. 19,277, filed concurrently with the instant application.

In the forml illustrated', the rotating hook and feed mechanism parts below the workbed extension A2 are not enclosed. When desired, they may be normally enclosed by an enclosure or guard member of known type mounted on the sewing machine for movement into and out of the position in which it covers the hook and feed mechanism.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, as set forth in the appended claims, and that in some cases certain features of my invention may be used to l advantage without a correspondinguse of other features. Y

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A sewing machine comprising in combination, a frame having a base, standard and arm portions, a hook shaft and a high speed motor with a rotating shaft mounted in said base portion, a speed reducing drive connection between said motor and hook shaft comprising a horizontal intermediate shaft mounted in said standard at a level between said base and arm, a speed reducing belt drive connection between said motor shaft and intermediate shaft, and a second speed reducing belt drive connection between said intermediate shaft and hook shaft, each of said belt drive connections having its lower portion in said base and having its upper portion in said standard.

2i. A sewing machine as specied in claim 1, in which said standard is formed with a wall opening substantially coaxial with said intermediate shaft and which includes a hand wheel detachably connected to said intermediate shaft and having a rim portion external to said standard, and in which the belt drive connection between said motor shaft and intermediate shaft is arranged and disposed in said frame to permit the withdrawal of the belt portion of said connecton from the frame through said wall openmg.

3. A sewing machine as specied in claim 1, in which one at least, of said belt drive connections comprises two grooved pulleys and an elastic belt running over said wheels.

4. A sewing machine as speciedA in claim 1, in which one, at least, of said belt drive connections comprises two toothed sprocket wheels and a tooth engaging belt running over said wheels.

5. A sewing machine as specied in claim l, comprising a needle actuating mechanism including a needle bar shaft journaled in said arm portion and a link extending through said standard between the said arm and base portions of the frame and connected to the last mentioned shaft for oscillating the latter, and in which the belt drive connection between said intermediate shaft and hook shaft comprises an element secured to and rotating with said hook shaft and forming a part of said second belt drive connection and a crank pin carried by said element 8 and connecting said element t said link Whereby the needle bar shaft is oscillated in timed relation with the rotation of the hook shaft. RICHARD K. HOI-IMANN.

REFERENCES CITED The following references are of record inthe le of this patent:

UNITED STATES PATENTS Number Name Date 1,525,643 Fifeld Feb. 10, 1925 1,841,933 Thompson Jan. 19, 1932 2,144,801 Hohmann Jan. 24, 1939 2,161,140 De Voe June 6, 1939 2,247,381 Hohmann et al July 1, 1941 2,276,246 Fleckenstein Mar. 10, 1942 2,318,442 Way et al May 4, 1943 2,413,277 Zeier Dec. 24, 1946 FOREIGN PATENTS Number Country Date 375,770 Italy Oct. 24, 1939 

